Heart attack signs vary by sex

“Heart attack symptoms differ in women,” BBC News has today reported. The broadcaster says that women having a heart attack are less likely to experience chest pain, compared with men.

A heart attack can cause a range of different symptoms, from crushing chest pains to tingling in the limbs, and feelings of breathlessness or nausea. Given the variations in possible symptoms, US researchers set out to examine just how common chest pain and discomfort is for each gender, and whether it indicate an increased risk that a patient might die. To do so, they examined records on more than 1 million US men and women who suffered from a heart attack between 1994 and 2006. The researchers looked for links between gender, symptoms and death rates.

Overall, 42% of men with a heart attack reported chest pain, compared with 30.7% of women. Further calculations revealed that the younger a woman was, the higher the chance she would not experience chest pain.

The results from this large pool of subjects helps demonstrate that although we perceive chest pain to be the key symptom of a heart attack, it isn't always present. People may also experience any combination of symptoms without any pain at all, such as shortness of breath, sweating and nausea. Although the study suggests that a heart attack without any pain (in the chest, arm, neck or jaw) may be slightly more common in women than men, raising awareness of the different possible signs of a heart attack is important for both sexes, so that when a heart attack is suspected people can receive emergency medical assistance as quickly as possible.

The study was carried out by researchers from Watson Clinic and Lakeland Regional Medical Center, Lakeland, Florida and various other academic and health institutions in the US. It was funded by Genentech, a company specialising in pharmaceuticals and biotechnology. The study was published in the peer-reviewed Journal of the American Medical Association (JAMA).

This was a cohort study that aimed to examine whether there is any difference between the heart attack symptoms experienced by men and women. The researchers conducting the study also looked at whether the relationship with gender is influenced by age, and whether there is any association between these factors and the risk of death while in hospital following a heart attack.

This sort of study can tell us how common it is (the prevalence) for men and women to experience a heart attack (known medically as a “myocardial infarction”) with or without chest pain symptoms. The research drew its subjects from a large, nationwide registry of heart attack patients called the National Registry of Myocardial Infarction. This would be a valuable source to use in a prevalence study, as its size and widespread use mean we can be fairly sure that the people within this study would be representative of all those who experience a heart attack. However, it can tell us little more than prevalence figures. For example, it can’t tell us the reasons for differences in symptoms between men and women.

The National Registry of Myocardial Infarction is reported to be the largest registry of its kind in the world, featuring records on more than 2 million patients with a heart attack admitted to 1,977 participating hospitals between 1994 and 2006. A diagnosis of a heart attack was based on clinician assessment and supporting information from investigations (such as heart attack markers on blood tests, electrocardiogram [ECG] evidence and autopsy findings). The researchers’ analysis excluded records from patients who were transferred to other hospitals, and patients who did not have complete records on gender, age or symptoms at the time they were first given medical attention. This left just over 1 million patients in their study, 42.1% of whom were women.

The researchers say that the only symptom recorded in the registry was the presence or absence of chest pain or discomfort. This pain could include:

The symptom was classed as present or absent before admission, during admission or at both times. People who were classed as having chest pain may or may not also have experienced additional symptoms such as shortness of breath, nausea or vomiting, heart palpitations, faintness or collapse. People who experienced any of these symptoms but without pain were simply classed in the "no pain" group and no further recording was made of the individual symptoms these people actually experienced. Therefore, the study can only tell us how many people experienced "pain" or "no pain"; it can’t tell us what the people without pain experienced instead (for example, how many were admitted with breathing difficulties, or following a collapse).

Statistical analyses were used to look at the presence or absence of chest pain or discomfort in relation to gender and age, with participants principally grouped according to whether they were older or younger than 65. The analyses were adjusted for the patients’ existing characteristics, such as their cardiovascular risk factors and their cardiac and general medical histories.

Women experiencing a heart attack were, on average, significantly older than men (73.9 years old compared with 66.5 years old). More men than women presented with the symptom of chest pain or discomfort (42.0% vs. 30.7%).

Further statistical analyses revealed that the younger a woman was, the slightly higher the odds that her heart attack would have presented without pain:

The researchers found that 14.6% of women and 10.3% of men died in hospital following their heart attack. Overall, there was a significant relationship between gender, symptoms, age and risk of death (mortality). When looking at trends in mortality by age-group, the researchers found that mortality tended to be higher among younger women (aged 54 or younger) who presented without chest pain than among men of a similar age who presented without chest pain.

Over the age of 54 the absence of chest pain was no longer associated with a greater risk of death for women compared with men (in other words, men and women without chest pain were at equivalent risk of death), and at the age of 65 and over women who presented without chest pain were actually less likely to die in hospital than men of a similar age and presentation.

The researchers concluded that in the national registry of patients hospitalised with heart attack, women were more likely than men to present without chest pain. They also said that men and women differ in how frequently they present without chest pain, and that the associated differences in heart attack mortality were “attenuated with age”. In other words, older men and women had fewer differences between each other in their presentation and mortality rates.

This study gives us an indication of the proportion of men and women who do or don’t experience chest pain or discomfort during a heart attack and whether this could be a potential indicator of a patient being at increased risk of death. That the data was taken from a large population registry of over 1 million people makes it a valuable source of information and we can be fairly confident that it’s representative of the general US population who would present to hospital with a heart attack.

The primary result of this study is that slightly more women than men experience heart attack without pain: 42% compared to 30.7% of men. However, it is not possible to say from this study why patients do or don’t experience chest pain. The researchers say that further studies into this would be necessary.

The study also found a trend for heart attack without pain to be more common among younger women than in younger men, but the difference between the two genders diminished with each increasing age category. Women aged under 45 were 38% more likely than men of the same age to experience a heart attack without symptoms, while women between the ages of 65 and 74 were only 13% more likely to. The researchers noticed a trend for higher mortality among younger women who presented without chest pain compared with younger men who presented without chest pain, but the associations within each age-group were not all large enough to be statistically significant. It's also worth noting that analyses of younger women with heart attacks involved smaller groups of women: around three-quarters of all women in this registry were over 65 when they had their heart attack, and the average age was 73.9. Analyses of smaller numbers of people may be less robust than those of larger numbers.

The results from this large cohort help to raise awareness among the general population that although we perceive chest pain to be the key symptom of a heart attack, this is not always the case. Although chest pain is a characteristic symptom during a heart attack (sometimes described as a heavy, crushing, pressing or squeezing pain), not all patients will experience it. Some people may feel pain, tingling or discomfort in one or both arms, the throat, jaw or back in addition to pains in the chest; and others may experience pain in only these locations with no pain in the chest. Sometimes the chest pain may only be mild discomfort and it may feel like heartburn. Other common symptoms that may be experienced – either with or without pain – are feeling short of breath, sweaty and clammy, feeling sick, or feeling faint or collapsing. Sometimes a heart attack can happen with no symptoms at all.

Although the study suggests that a heart attack without pain (chest, arm or jaw) may be slightly more common in women than men, raising awareness of the different possible symptoms of a heart attack is equally important in both genders, so that emergency medical assistance can be sought as quickly as possible if heart attack is suspected.